Ultraviolet photoreactor for the purification of fluids

Abstract

In order to disinfect and to detoxify a fluid, a photoreactor contains at least two light sources. One light source activates the catalytic function of a semiconductor material in the fluid to reduce the concentration of contaminants in the fluid, such as by breaking down organic contaminants into non-toxic compounds. A second light source acts directly on living biological entities to sterilize or kill them and thereby disinfect the fluid, and can also serve to activate a semiconductor photocatalyst that in turn causes further damage to biological contaminants. The semiconductor photocatalyst is desirably attached to an optically transmitting fiber substrate in the fluid. The second light source in one embodiment is external to the fluid and illuminates the photocatalyst through transmitting surfaces in a fluid containment vessel. The light sources can comprise respective sets of plural LEDs.

We claim: 
     
       1. An apparatus for treating fluid comprising:
 a housing comprising an inlet for receiving fluid to be treated and an outlet for delivering treated fluid, the housing defining a fluid flow path between the inlet and the outlet; 
 a light transmitting fiber substrate in the fluid flow path; 
 a semiconductor photocatalyst adhered to the substrate, the photocatalyst comprising at least a first photocatalyst with a first band gap wavelength; 
 at least one first light source operable to deliver light to fluid in the housing to be treated, said at least one first light source emitting at least one first band of light having a center wavelength in the range from 250 nanometers to 285 nanometers so as to provide disinfection treatment of the fluid; and 
 at least one second light source operable to deliver light to the photocatalyst in the fluid in the housing to be treated, said at least one second light source emitting at least one second band of light having a center wavelength at or below the first band gap wavelength so as to provide a photocatalytic reduction of contaminant concentrations in the fluid. 
 
     
     
       2. An apparatus according to  claim 1  wherein said at least one first light source comprises a first set comprising a plurality of LED light sources operable to emit light at a wavelength in a first band centered at a first wavelength and having a full width half maximum band that is at least ten nanometers wide. 
     
     
       3. An apparatus according to  claim 1  wherein all of the light sources included in the at least one first light source are operable to deliver energy to the fluid in the housing at a level of no less than 10 millijoules per square centimeter. 
     
     
       4. An apparatus according to  claim 1  wherein the photocatalyst comprises at least first and second semiconductor photocatalysts. 
     
     
       5. An apparatus for treating fluid comprising:
 a housing comprising an inlet for receiving fluid to be treated and an outlet for delivering treated fluid, the housing defining a fluid flow path between the inlet and the outlet; 
 a light transmitting substrate in the fluid flow path; 
 a semiconductor photocatalyst adhered to the substrate, the photocatalyst comprising at least a first photocatalyst with a first band gap wavelength; 
 at least one first light source operable to deliver light to fluid in the housing to be treated said at least one first light source emitting at least one first band of light having a center wavelenghth in the range from 250 nanometers to 285 nanometers so as to provide disinfection treatment of the fluid; 
 at least one second light source operable to deliver light to the photocatalyst in the fluid in the housing to be treated, said at least one second light source emitting at least one second band of light having a center wavelenghth at or below the first band gap wavelength so as to provide a photocatalytic reduction of contaminant concentrations in the fluid; and 
 wherein the housing comprises a plurality of chambers, each chamber containing light transmitting substrate with photocatalyst adhered to the substrate, the housing defining a fluid flow path from the inlet through the chambers to the outlet, the apparatus comprising at least three concentric annular chambers comprising right cylindrical chamber walls, the exterior most chamber wall comprising a light reflective material, the other cylindrical walls comprising light transmissive material, an interior lamp receiving chamber being provided within the interior of the innermost annular chamber for receiving at least one first light source, said at least one first light source comprising a low pressure mercury lamp, the at least one second light source comprising a plurality of LED light sources mounted to the walls of the annular chambers. 
 
     
     
       6. An apparatus according to  claim 5  wherein the LED light sources are positioned in light transmitting tubes mounted within at least one chamber. 
     
     
       7. An apparatus according to  claim 6  wherein the tubes comprise flexible material which is spirally disposed within at least one of the chambers. 
     
     
       8. An apparatus according to  claim 7  wherein the tubes are of a light transmitting fluorinated ethylene propylene (FEP). 
     
     
       9. An apparatus according to  claim 8  wherein the light transmissive material is selected from the group consisting of glass, silica, quartz and fluorinated ethylene propylene. 
     
     
       10. An apparatus for treating fluid comprising:
 a housing comprising an inlet for receiving fluid to be treated and an outlet for delivering treated fluid, the housing defining a fluid flow path between the inlet and the outlet; 
 a light transmitting substrate in the fluid flow path; 
 a semiconductor photocatalyst adhered to the substrate, the photocatalyst comprising at least a first photocatalyst with a first band gap wavelength; 
 at least one first light source operable to deliver light to fluid in the housing to be treated said at least one first light source emitting at least one first band of light having a center wavelength in the range from 250 nanometers to 285 nanometers so as to provide disinfection treatment of the fluid; 
 at least one second light source operable to deliver light to the photocatalyst in the fluid in the housing to be treated, said at least one second light source emitting at least one second band of light having a center wavelength at or below the first band gap wavelength so as to provide a photocatalytic reduction of contaminant concentration in the fluid; and 
 comprising at least one elongated optical wave guide extending into the interior of the housing from a first location, at least one of the first and second light sources being optically coupled to the at least one elongated wave guide with the wave guide guiding light from the said at least one optically coupled light source into fluid in the housing. 
 
     
     
       11. An apparatus according to  claim 10  wherein said at least one wave guide comprises a wall surface and wall surface modifications that diffuse light passing along the wave guide outwardly from the wave guide through the wall surface. 
     
     
       12. An apparatus according to  claim 11  wherein said surface modifications comprise one or more of a surface coating, chemical etchings, mold-texturing, photo-ablation, and sand blasted regions.